Hello,
I am Anthony Basile. I have recently shifted to Linux OS and facing issues in themes. Is there any theme available for the Linux?
What distro are you using? What issues do you have with it? I use the compact dark theme that is built into FIrefox DevEdition with Arc theme on Unity/Gnome.
https://addons.mozilla.org/en-US/firefox/search/?q=Arc
Also if you are using dark themes for GTK check out this addon https://addons.mozilla.org/en-US/firefox/addon/text-contrast-for-dark-themes/